Apparatus and method for decoding in communication system

Abstract

An apparatus and a method for decoding bits of a received signal in a communication system are provided. The method includes determining path metrics of respective states in a trellis corresponding to the received signal, selecting a start state in the trellis for a traceback in a last window of the trellis, repeating the traceback at least twice within the last window, and when the repeating of the traceback is completed, determining the decoded bits of the received signal using a survived path of a last traceback.

What is claimed is: 
     
       1. A method for decoding bits of a received signal in a communication system, the method comprising:
 determining path metrics of respective states in a trellis corresponding to the received signal; 
 selecting a start state in the trellis for a traceback in a last window of the trellis; 
 consecutively repeating the traceback at least twice within the last window; and 
 determining the decoded bits of the received signal using a survived path of a last traceback after the repeating of the traceback is completed. 
 
     
     
       2. The method of  claim 1 , wherein the start state for the traceback is a state of the trellis having a maximum path metric. 
     
     
       3. The method of  claim 1 , wherein the start state for the traceback is a state having a value of 0. 
     
     
       4. The method of  claim 1 , further comprising:
 storing traceback information for a traceback corresponding to a current state in the trellis; and 
 discarding traceback information for a traceback corresponding to a state in the trellis in a window other than the last window of the trellis. 
 
     
     
       5. The method of  claim 4 , wherein the discarding of the traceback information for the traceback corresponding to the state in the window other than the last window comprises overwriting current traceback information with the traceback information corresponding to a state of the last window of the trellis. 
     
     
       6. The method of  claim 4 , wherein the storing of the traceback information comprises storing no more than traceback information corresponding to one window the trellis. 
     
     
       7. The method of  claim 1 , wherein the path metrics are determined for each of a plurality of windows, and
 wherein the traceback is repeated as many times as a number of the plurality of the windows. 
 
     
     
       8. The method of  claim 1 , wherein the repeating of the traceback from the start state at least twice within the last window comprises performing the traceback from a last state of a previous traceback in a last column of the trellis. 
     
     
       9. The method of  claim 1 , further comprising determining whether the decoding is successful according to whether a start state and an end state of the traceback are identical after the repeating of the traceback at least twice is completed. 
     
     
       10. The method of  claim 9 , wherein it is determined that the decoding is not successful if the start state and the end state of the traceback are not identical. 
     
     
       11. An apparatus for decoding bits of a received signal in a communication system, the apparatus comprising:
 a calculator for determining path metrics of respective states in a trellis corresponding to the received signal; 
 a tracer for selecting a start state in the trellis for a traceback in a last window of the trellis, and consecutively repeating the traceback at least twice within the last window; and 
 a determiner for determining the decoded bits of the received signal using a survived path of a last traceback after the repeating of the traceback is completed. 
 
     
     
       12. The apparatus of  claim 11 , wherein the start state for the traceback is a state of the trellis having a maximum path metric. 
     
     
       13. The apparatus of  claim 11 , wherein the start state for the traceback is a state having a value of 0. 
     
     
       14. The apparatus of  claim 11 , further comprising a memory for storing traceback information, and discarding the traceback information for a traceback corresponding to states in the trellis in a window other than a state of the trellis of the last window of the trellis. 
     
     
       15. The apparatus of  claim 14 , wherein the memory overwrites current traceback information with the traceback information corresponding to the state of the last window of the trellis. 
     
     
       16. The apparatus of  claim 14 , wherein the memory stores no more than traceback information corresponding to one window the trellis. 
     
     
       17. The apparatus of  claim 11 , wherein the path metrics are determined for each of a plurality of windows, and
 wherein the traceback is repeated as many times as a number of the plurality of the windows. 
 
     
     
       18. The apparatus of  claim 11 , wherein the tracer performs the traceback from a last state of a previous traceback in a last column of the trellis. 
     
     
       19. The apparatus of  claim 11 , wherein the determiner determines whether the decoding is successful according to whether a start state and an end state of the traceback are identical after the repeating of the traceback at least twice is completed. 
     
     
       20. The apparatus of  claim 19 , wherein it is determined that the decoding is not successful if the start state and the end state of the traceback are not identical. 
     
     
       21. The method of  claim 1 , wherein the last window comprises fixed path metrics. 
     
     
       22. The apparatus of  claim 11 , wherein the last window comprises fixed path metrics.